1. Field of the Invention
The present invention relates generally to the field of paper feeding apparatus for printers, and, more particularly, to apparatus for feeding a continuous web of fan-fold paper to high speed commercial printers, such as computer-driven laser printers.
2. Background Discussion
High speed laser printers capable of utilizing fan-fold, pin-feed forms are often used to process large quantities of information from a computer to printed forms. Banks, large medical facilities, investment houses, universities, and governmental agencies are typical users of these high speed, complex, and costly printing systems. The IBM 3800, Siemens 2200 and 2300, Storage Technology 6100, Unysis 0777, and Datagraphix 9800 are examples of such printers used in these print-intensive data centers when both print quality and speed are required. These printers have paper feed rates of either 100 or 200 feet per minute, (depending on the model) and can provide the highest through-put potential available today.
However the through-put potential of these printers cannot be completely realized because the paper storage bin, from which the fan-fold paper is supplied to the printer is recessed within the printer and will accept only one stack (about 2000 sheets) of fan-fold computer paper. During operation of the printer, this paper is automatically fed upwardly from the paper bin into and through the printing portion of the printer by a tractor drive mechanism. When the stack of paper of depleted, the print processing stops until another stack of paper is loaded into the paper bin and spliced onto the tail portion of the just-used stack. The printer down-time for such paper loading and splicing is typically about 4-5 minutes, or more, depending on when the operator can free himself or herself from other important tasks.
It can readily be calculated that a printer that prints at the rate of 200 feet per minute will deplete a 2000 sheet stack of paper in about 10 minutes. Thus the printer down-time for loading and splicing paper represents at least about 30 percent loss in potential through-put of the printer.
Moreover, to minimize such printer down-time, an operator must be at stand-by when the paper supply in the printer paper bin is running low so as to be immediately ready to load and splice in another stack. Thus data center functions are distrupted and operator efficiency is reduced.
In addition, these printers cost about $300,000 each; therefore, this paper replenishing down-line represents a considerable waste not only of printing time but of capital expenditures, the latter because it takes four printers to do the work which three could do if paper replenishing down-line could be eliminated or substantially reduced.
For the above-mentioned reasons, as well as other reasons, attempts have been made to provide auxiliary paper feeding apparatus for feeding a continuous web of fan-fold computer paper from a source of paper outside the printer to the normal paper feeding regions within the printer. By so providing, the splicing of one stack of forms to another can be accomplished while the printer is running, thereby eliminating the costly down-time described above. Exemplary of such auxiliary paper feeding apparatus are those disclosed in U.S. Patent No. Re. 31,210 to Lapp, et al.; U.S. Pat. No. 4,848,634 to Crowley, et al.; U.S. Pat. No. 4,564,184 to Rumpel; and U.S. Pat. No. 4,813,357 to Ward, et al.
As can be readily appreciated, the type of paper web routing required by such disclosed auxiliary paper feeding apparatus in and of itself presents serious paper feeding and control problems. In order to feed a continuous web of paper from an external paper source region, the auxiliary paper feeder must provide a means by which the web is made to change direction several times. To accomplish this, a series of turn bars can be arranged so as to deflect and redirect the flow of paper from the external source into the tractor drive mechanism of the associated printer.
A problem, however, exists with the use of stationary turn bars. The problem is that as the web of paper is redirected and comes into contact with the turn bars, there results a significant and often substantial drag on the paper. In some instances this drag on the paper web may be great enough to tear apart adjacent sheets of paper, thereby disrupting the paper feeding operation until the torn-apart sheets are spliced back together. Consequently, auxiliary paper feeding apparatus for high speed laser printers are known to use rotatably-driven turn bars as well as stationary turn bars so as to reduce the drag on the paper web as it changes direction over these turn bars.
One known example of such hybrid paper feeding apparatus utilizing both stationary and rotatably-driven turn bars is disclosed in the above-mentioned Lapp, et al., reissue patent. The auxiliary paper feeding apparatus as described therein is constructed for causing the moving web of paper to change direction four times by use of two stationary turn bars and two rotatably-driven turn bars.
However the providing of power-driven turn bars does not solve all the problems associated with reliably feeding a continuous web of fan-fold paper from an auxiliary feeder into an associated high sped printer. The drive belts used to drive the power-driven rollers are, for example, are a constant source of problems. For reliable performance, these belts must be adjusted when they become worn and loose and must be replaced when broken. Still further, the bearings used in the power-driven turn bars require periodic maintenance. Even further, the exposed power-driven turn bars and rollers present a work hazard to operators whose loose clothing, hair or fingers may become entangled in the drive belts or between the rotating turn bars and their associated paper guide plates.
Therefore, it would be desirable to provide a method and apparatus to guide a continuous web of paper from an external paper source to the normal feed path inside a printer without the use of power-driven turn bars so as to eliminate the maintenance, safety and performance problems associated with that tension (i.e., drag) reducing method.
Another problem typically encountered in any of the above-described printers and/or auxiliary paper feeders is the necessity for accurately splicing the top sheet of a fresh stack of forms to the tail end of the just-used stack. Such splices must be made carefully because they are critical to good printer performance. If a paper jam results from a poor paper splice, printer processing is disrupted, all pieces of the damaged form must be carefully removed from the printer and a new splice must be made.
Yet another problem with existing high speed printers of the type discussed above is that the splicing and threading of fresh stacks of forms must take in the recessed paper storage region of the printers. Personnel performing these tasks are required to work in cramped and awkward quarters, thereby increasing the chances for a poor splice.
For the above-mentioned reasons and others, it is desirable for any auxiliary paper feeding apparatus to provide an associated splicing method and apparatus for quick, accurate splicing of one stack of paper to another at an easily accessed, external paper source region.
It is, therefore, a principal objective of the present invention to provide an auxiliary feeding apparatus for feeding a continuous web of paper, especially fan-fold paper, to high speed computer printers, such as laser printers, and which employs turn bars which provide minimum drag on the web of paper changing the direction of travel thereover without using free-wheeling or power-driven rollers and turn bars. It is another objective of the present invention to provide for automatic feeding of stacks of paper to be fed into the associated printer and to provide easy means for splicing the leading end of one stack of paper to the tail end of the preceding stack of paper so as to maintain a continuous feeding of paper into an associated printer.